(a) Field
The present invention relates to a fuel cell stack, a membrane-electrode assembly, and a fabricating method of a membrane-electrode assembly.
(b) Description of the Related Art
As known, a fuel cell is configured as an electronic generator system that converts chemical reaction energy of hydrogen contained in hydrocarbonaceous fuel with separately supplied oxygen into electrical energy.
The fuel cell may be largely classified into polymer electrolyte membrane fuel cell and direct oxidation fuel cell.
The polymer electrolyte membrane fuel cell is typically configured as a fuel cell main body called a stack and is configured to have a structure that generates electrical energy by an electrochemical reaction of hydrogen supplied from a reformer with oxygen supplied by the operation of an air pump or a fan.
Unlike a polymer electrolyte membrane fuel cell, a direct oxidation fuel cell is configured to have a structure that directly receives fuel without using hydrogen and generates electrical energy by electrochemical reaction hydrogen contained in the fuel with separately supplied oxygen.
In the above-mentioned fuel cell, the stack is configured by stacking a unit cell including a plurality of membrane-electrode assemblies (MEA) and separators.
The membrane-electrode assembly includes a polymer electrolyte membrane, a pair of catalytic layers located on both sides of the polymer electrolyte membrane, and a gas diffusion layer formed on the catalytic layer. In addition, edge protective layers are located at the edges of the polymer electrolyte membrane, wherein the edge protective layers are located at the outside of the catalytic layers.
When the gas diffusion layer directly contacts the polymer electrolyte member due to a gap generated between the edge protective layer and the catalytic layer, the edge portion of the gas diffusion layer protrudes into the polymer electrolyte membrane. Deterioration may occur at this portion such that pin-holes can be generated in the electrolyte membrane. In addition, gas transmits at a portion where the gas diffusion layer directly contacts the polymer electrolyte membrane, such that the pin-holes may occur in the electrolyte membrane by hydration (—OH) radical generated by the combination of hydrogen and oxygen. For this reason, when the pin holes are generated in the polymer electrolyte membrane, the performance of the fuel cell can be suddenly deteriorated and power generation may cease during the operation of the fuel cell.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.